Your JComments is 3.05 and not adapted to PHP 7.2.8. At Github there is a version 3.0.7 adapted for php 7. 3.07 is a security fix also.viewtopic.php?f=715&t=962931&start=30
Your max_execution_time 3000 is high. I always use 30.

The hotlinked image that slowed down was on my site and not yours. But I think you should check the database values in Joomla administration. You migh have wrong value there. Check first what your web hotel recommends and then what you actually have.